Eating carbohydrate-rich foods before or during prolonged exercise can delay the onset of fatigue and improve endurance or performance. It’s important for maintaining blood sugar levels in events lasting more than an hour. Carbohydrate-rich beverages are especially useful during the later stages of exercise when muscle glycogen levels are significantly reduced. (Glycogen is the storage form of carbohydrate in the body and is found in the liver and muscle.)
Many popular sports beverages contain both protein and carbohydrate. However, it’s not clear that the addition of protein improves athletic performance.
Researchers in Malaysia studied the effects of soy protein on athletic performance in male recreational cyclists. The subjects consumed a drink based on sago, a starch extracted from palm stems and a commonly consumed food in India and Malaysia with or without the addition of 15 grams of soy protein. A control group drank a noncalorically-sweetened beverage.
After consuming the beverages, study participants cycled for 60 minutes on a cycle ergometer at 60% of their maximum speed, followed by a time-to-exhaustion ride at 90% of their maximum. A cycle ergometer is a stationary one-wheeled cycle that measures work output under controlled conditions.
The time to exhaustion for cyclists when they were given the placebo was 4.09 minutes. In those subjects drinking the plain sago drink, time to exhaustion was 5.49 minutes (34% increase), indicating that the carbohydrate alone enhanced performance. However, when consuming the combination of soy protein and sago, the time to exhaustion was 7.53 minutes, which represents 84% increase compared to the placebo alone. The authors of this study concluded that a combination of sago and soy protein can delay fatigue during high-intensity cycling.
Ghosh AK, Rahaman AA, Singh R. Combination of sago and soy-protein supplementation during endurance cycling exercise and subsequent high-intensity endurance capacity. Int J Sport Nutr Exerc Metab 2010;20:216-23.